Proper evaluation in the laboratory of the efficacy of various circulatory assist methods and devices used clinically in the treatment of cardiogenic shock has not been possible because an acceptable model for study has not been available. The left circumflex coronary artery is the dominant artery of the left ventricle in the dog and ligation results in localized ischemic myocardial damage without interrupting venous return from the involved area, without compromising existing collaterals, and without introducing the multiple effects of neurohumoral isolation of the heart by pharmacological means. It has been possible to ligate the circumflex artery proximally with an incidence of ventricular fibrillation of 7.8 percent whereas the usual rate is above 60 percent within the first hour; 45 percent of the left ventricular muscle mass was infarcted. To our knowledge these studies present information for the first time obtained in dogs in which the circumflex artery has been ligated proximally. It is anticipated that this model will be used for multiple purposes including the evaluation of various methods and devices used in the treatment of cardiogenic shock.